The disclosures herein relate generally to fuel dispensers and more particularly to multiple grade fuel dispensers which deliver different grade fuel from separate storage tanks.
Multiple grade fuel dispensers, of the type commonly used at gas stations, have a plurality of hoses with delivery nozzles at each dispenser unit. Each nozzle delivers a different grade of fuel from a storage tank in the ground. There is usually no actual pump in the dispenser unit. Instead, a submersible pump is located in each tank. When a product is selected at the dispenser, the pump will engage and pressurize the fuel line, and the fuel will flow through the line and go to the designated dispenser.
In the typical system including several multiple grade dispensers, there is usually a main feeder pipe from the storage tank for each grade. Several branch lines link the main feeder pipe with each dispenser. There is only one pump for each storage tank however, which supplies multiple dispensers. This requires a system to allow each dispenser to access the pump. This is accomplished by, for example, a 120 volt AC line connecting the dispenser to a relay which feeds power to the submersible pump located in the storage tank, see FIG. 1. Each dispenser that uses a particular storage tank will have a 120 volt line connected in parallel with the other lines to that relay. As long as there is at least one dispenser using a storage tank, the respective relay will remain engaged. Therefore, a three hose dispenser, i.e., a dispenser which dispenses three grades of fuel, requires three separate 120 volt lines feeding back to a common location, usually located inside the gas station, operably connected to a relay associated with each pump. With the requirement that power for the fuel tank submersible pump relays be supplied by the dispensers, and an individual wire for each tank that is to be controlled, each dispenser is a potential failure point.
Each dispenser carries a serial communication data link which is used by the site controller, cash register, or whatever, to exchange information with the dispenser. Some of the information identifies what the product is, i.e., which grade of fuel. The site controller is able to detect which tank will be accessed when a product is selected, but each dispenser believes it is the only user of a tank.
Thus, present systems include dispensers located at various service islands, the indoor site controller, the communication link interconnecting all of the dispensers with the site controller, each dispenser having a wire connected to the relay to pass power to the submersible pump.
It would be beneficial to shift the responsibility for turning on the submersible pump relay from the dispenser to the site controller. This would eliminate the need for individual submersible pump control wiring from the dispensers to the pump control relays and would simplify dispenser installation, reduce product costs and diminish problems associated with AC voltage feeding back to the dispensers from the relays. Also, it would be beneficial to be able to retro-fit present installations to use existing hardware to function in this manner without the need to install new re-wiring arrangements between the dispensers and the site controller.
Therefore, what is needed is a method and apparatus which provides that the site controller have the ability to detect product selection at the fuel dispenser which results in a change in the state of the submersible pump located in the storage tank holding the selected product. The site controller can then pass the selection information over the serial data link to control the relays and turn the submersible pumps on and off as necessary to control fuel delivery to the dispensers.